Method and apparatus for recording time information for digital data streams

ABSTRACT

A recording medium, an apparatus and a method for recording time information of digital data streams are provided. The apparatus in one embodiment includes a time information creating unit creating a first time field and a second time field, wherein the first time field includes a 90 KHz unit value and the second time field includes a 27 MHz unit value, and a data formatter creating a data object unit being presentation data by adding a corresponding unit of the digital data to management data including the time information.

CROSS-REFERENCE

The present application is a continuation of co-pending U.S. patentapplication Ser. No. 10/728,945 filed Dec. 8, 2003, which is acontinuation of co-pending U.S. patent application Ser. No. 10/376,254filed on Mar. 3, 2003 (now U.S. Pat. No. 6,771,724 issued on Aug. 3,2004) for which priority is claimed under 35 U.S.C. §120, which is acontinuation of co-pending U.S. application Ser. No. 09/410,755 filed onOct. 1, 1999, now issued as U.S. Pat. No. 6,553,086, for which priorityis claimed under 35 U.S.C. §120; and the present application claimspriority of Patent Application No. 98-41937 filed in Korea on Oct. 2,1998 and Patent Application No. 99-4467 filed in Korea on Feb. 9, 1999,under 35 U.S.C. §119. The entire contents of each of these applicationsare herein fully incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for recordingand transferring time information for digital data streams. A digitaldata stream is recorded on a recording medium along with the timeinformation thereof and thus every packet stream unit has the timeinformation of its own. The time information is used for searching therecording medium for a specific packet stream unit requested by a userand maintaining a precise timing for transferring packet stream unitsthrough a digital interface to an external apparatus.

2. Description of the Related Art

In conventional analog television broadcast, video signals aretransmitted over the air or through cables after being AM or FMmodulated. With the recent rapid advance of digital technologies such asdigital image compression or digital modulation/demodulation,standardization for digital television broadcast is in rapid progress.Based upon the Moving Picture Experts Group (MPEG) format, satellite andcable broadcast industry also moves towards digital broadcast.

Digital broadcast offers several advantages that its analog counterpartcannot provide. For example, digital broadcast is capable of providingservices with far more improved video/audio quality, transmittingseveral different programs within a fixed bandwidth, and offeringenhanced compatibility with digital communication media or digitalstorage media.

In digital broadcast, a plurality of programs encoded based upon theMPEG format are multiplexed into a transport stream before transmitted.The transmitted transport stream is received by a set top box at thereceiver and demultiplexed into a plurality of programs. If a program ischosen from among the demultiplexed programs, the chosen program isdecoded by a decoder in the set top box and original audio and videosignals are retrieved. The retrieved audio and video signals can bepresented by an A/V output apparatus such as a TV.

It is also possible to store the received digital broadcast signals on astorage medium instead of directly outputting the received broadcastsignals to A/V output devices. The stored digital broadcast signals canbe edited and presented afterwards. For example, a digital data streamreceived by a set top box can be stored in a streamer such as a digitalvideo disk (DVD) through communication interfaces like an IEEE-1394serial bus. Later, the stored digital data stream can be edited andtransmitted back to the set top box so that the original digital audioand video data can be presented.

When recording the digital data stream of a single program in astreamer, the basic recording unit is the stream object (SOB) comprisinga series of stream object units (SOBUs). To record received digitalbroadcast signals in a streamer and reproduce the recorded signalsafterwards, it is necessary to explore how to group and record streamobjects (SOBs) and stream object units (SOBUs) and how to create searchinformation for managing and searching for the recorded stream objects(SOBs) and stream object units (SOBUs) Also, it is required toinvestigate how to search a specific data stream corresponding to asearch time requested by a user.

A conventional method for recording digital data streams and creatingand recording navigation information will now be explained withreference to the accompanying drawings.

FIG. 1 depicts a block diagram of an apparatus in which the conventionalmethod for creating and recording the navigation information of adigital data stream can be employed. FIG. 2 depicts the process ofrecording the digital data stream and creating the navigationinformation in the system shown in FIG. 1. The system comprises a settop box 100, a communication interface (IEEE-1394), and a streamer 200.The set top box 100 receives transport streams encoded by systemencoders and broadcast by a plurality of broadcast stations, anddemultiplexes the received transport streams. After a decoder 120decodes the transport stream of a program tuned by a tuning unit 110, acontrol unit 140 outputs the decoded transport stream to an A/V outputapparatus or to the streamer 200 through an IEEE-1394 communicationinterface 130 and 210 so that the transmitted program can be recorded inthe streamer 200, depending upon a user's request. When requested by auser, the streamer 200 retrieves the recorded program and transmits theretrieved program through the IEEE-1394 communication interface back tothe set top box 100. In the set top box 100, the received program isdecoded by the decoder 120 and outputted to an A/V output apparatus sothat the recorded program can be presented.

A control unit 250 in the streamer 200 controls the data streamtransmitted from set top box 100 to be recorded as shown in FIG. 2 on arecording medium 230 by a recording stream processing unit 220. Thereceived data stream including transport stream packets is recorded onthe recording medium along with the packet arrival time (PAT) of eachtransport stream packet, wherein the packet arrival time will be used asa time reference for transmitting the associated transport packet inplayback. In the streamer 200, the transport stream packets with packetarrival times are organized in sectors with each sector having apredetermined size. A predetermined number of sectors, for example 32sectors, are grouped into a stream object unit (SOBU). If the recordingprocess is stopped or suspended by a user, the recorded stream objectunits (SOBUs) are organized into a stream object (SOB). Additionally,navigation data such as the stream start application packet arrival time(S_S_APAT) and incremental application packet arrival time (IAPAT) forsearching for and managing the stream object (SOB) and stream objectunits (SOBUs) is recorded together on the recording medium.

FIG. 3 shows the way the received digital data stream is recorded in thestreamer 200. An application packet and a packet arrival time (PAT ortime stamp) constitute a transport stream packet (TSP). A plurality oftransport stream packets (TSPs) and a header are organized into a sectorand a predetermined number of sectors, for example 32 sectors,constitute a stream object unit (SOBU). A series of stream object units(SOBUs) constitutes a stream object (SOB). Meanwhile, the stream objectinformation (SOBI), which is the navigation data for managing andsearching for the recorded stream objects (SOBs), comprises a streamobject general information (SOB_GI) and a mapping list (MAPL) formanaging stream object units (SOBUs), as shown in FIGS. 4 and 5. Thestream object general information (SOB_GI) includes the stream startapplication packet arrival time (S_S_APAT) indicative of the start timeof the associated stream object (SOB). As shown in FIG. 2, theincremental packet arrival time (IAPAT), which is a count value countedat constant time intervals (x) between two consecutive stream objectunits (SOUBs), is included in the mapping list (MAPL) and used asinformation for searching for the stream object (SOB) and stream objectunits (SOBUs) afterwards.

The stream start packet arrival time (S_S_APAT) contained in the streamobject general information (SOB_GI) is recorded as a 6-byte packetarrival time (PAT) comprising a 9-bit packet arrival time extension(PAT_ext) and 39-bit packet arrival time base (PAT_base), as shown inFIG. 6A. The packet arrival time extension (PAT_ext) is a modulo-300counter that is incremented at a rate of 27 MHz, whereas the packetarrival time base (PAT_base) is incremented at a rate of 90 kHz. Unlikeformat of the stream start application packet arrival time (S_S_APAT),the time stamp recorded along with the application packet shown in FIG.3 is recorded as a 4-byte packet arrival time (PAT), shown in FIG. 6B,that is incremented at a rate of 27 MHz and can represent from 0 s up to159 s (=232/27 MHz).

The method for searching a digital data stream corresponding to arequested search time using the navigation and time informationregarding the stream objects (SOBs) and stream object units (SOBUs) willbe explained in detail with reference to an example.

With reference to FIG. 2, suppose that the position(s) of a transportstream packet corresponding to a search time (ST) requested by a user isto be searched for. First, the stream start application packet arrivaltime (S_S_APAT) contained in the stream object general information(SOB_GI) of each stream object (SOB) is compared with the requestedsearch time (ST) and a stream start application packet arrival time(S_S_APAT) that is closest to but does not exceed the request searchtime (ST) is detected.

Referring to the mapping list (MAPL) of the stream object SOB #1corresponding to the detected stream start application packet arrivaltime (S_S_APAT), the incremental application packet arrival times (IAPAT1˜4) contained in the mapping list (MAPL) are summed up. The sum valueis multiplied by the unit time (x) and added to the detected streamstart application packet arrival time (S_S_APAT). The procedure isrepeated until the calculated value (S_S_APAT+x×Σ IAPAT) approaches therequested search time (ST) without exceeding it. In FIG. 2, thesummation and multiplication is repeated to include IAPAT 4 because thecalculated value exceeds the search time (ST) if the calculationcontinues to IAPAT 5. Then the entry in the mapping list (MAPL)corresponding to the calculated time (S_S_APAT+x×Σ IAPAT) is located andthe index of the entry is multiplied by the number of sectorsconstituting a stream object unit (for example, 32 sectors) to locatethe desired stream object unit SOBU 5.

From the start position A′ of the searched stream object SOBU 5, the4-byte packet arrival time (PAT), which is the time stamp of thetransport stream packet, is detected. Recall that the stream startapplication packet arrival time (S_S_APAT) and the packet arrival time(PAT) of a transport stream packet have different formats and thereforethe two values cannot be compared directly. For this reason, thedifference between the detected packet arrival time (PAT) and the packetarrival time of the first transport stream packet of the stream objectunit SOBU 5 is compared with the difference between the requested searchtime (ST) and the calculated value (S_S APAT+x×Σ IAPAT) for fine searchof the transport stream packet corresponding to the requested searchtime (ST).

The position A searched based upon the time information (S_S_APAT+x×ΣIAPAT) calculated using the incremental application packet arrival times(IAPATs), however, does not coincide with the actual start position A′of the stream object unit SOBU 5, as shown in FIG. 2. The offset betweenthe transport stream packet position A detected by the fine searchoperation and the actual position A′ results in a delay in the searchoperation.

As a result, additional information indicative of the offset valuebetween A′ and A (Offset_SZ in FIG. 2) is necessary for preciselysearching for the position(s) of the transport stream packetcorresponding to the requested search time (ST). It is not desirable,however, to add the additional information to every stream object unit(SOBU), which dramatically lowers the recording efficiency of therecording medium.

The digital data communication between the set top box 100 and thestreamer 200 is conducted through an IEEE-1394 digital communicationinterface. The IEEE-1394 interface inserts a time stamp of a frequencyof 24.576 MHz into each transport stream packet before transmitting thetransport stream packets for guaranteeing real-time digital datacommunication.

As explained before, the streamer 200 also adds time stamps of afrequency of 27 MHz to the transport stream packets of the recorded datafor presentation. Since the clock used by the streamer 200 differs fromthat used by the IEEE-1394 interface, the time information of thetransport stream transmitted through the IEEE-1394 interface based upona 24.576 MHz clock may become different from that of the streamer 200based upon a 27 MHz clock, which may cause critical problems such asskipped presentation of video data.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method andapparatus for creating and recording time information intended forprecisely searching a recording medium for a requested packet streamunit. When recording received packet stream units on a recording medium,time information pertaining to each of the received packet stream unitis created and added to the corresponding packet stream unit. The formatof the added time information is compatible with a search time requestedby a user so that the timing error that may arise in search operationscan be effectively eliminated.

It is another object of the present invention to provide a method andapparatus for creating and recording arrival time information of eachpacket stream unit so that the arrival time added to each of thereceived transport stream unit when recording received packet streamunits is synchronized with the clock used in digital interfaces

In accordance with an aspect of the present invention, there is providedan apparatus for recording time information associated with digitaldata, comprising a time information creating unit creating a first timefield and a second time field, wherein the first time field includes a90 KHz unit value and the second time field includes a 27 MHz unitvalue; and a data formatter creating a data object unit beingpresentation data by adding a corresponding unit of the digital data tomanagement data including the time information.

In accordance with an aspect of the present invention, there is provideda method of recording time information associated with digital data,comprising creating a time information including a first time field anda second time field, wherein the first time field includes a 90 KHz unitvalue and the second time field includes a 27 MHz unit value; andcreating a data object unit being presentation data by adding acorresponding unit of the digital data to management data including thetime information.

In accordance with an aspect of the present invention, there is provideda recording medium including time information associated with digitaldata, comprising a recording layer; and data object units recorded onthe recording layer, wherein the data object units being presentationdata are created by adding a corresponding unit of the digital data tomanagement data including a time information, wherein the timeinformation includes a first time field and a second time field, whereinthe first time field includes a 90 KHz unit value and the second timefield includes a 27 MHz unit value.

In accordance with an aspect of the present invention, there is provideda method of reproducing digital data, comprising (a) reading managementdata associated with a data object unit including video presentationdata, wherein the management information includes a time informationcomprising a first time field and a second time field, and the firsttime field includes a 90 KHz unit value and the second time fieldincludes a 27 MHz unit value; and (b) reproducing the data object unitbased on the time information.

These and other objects of the present application will become morereadily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modification within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate the preferred embodiments ofthe invention, and together with the description, serve to explain theprinciples of the present invention.

In the drawings:

FIG. 1 is a block diagram of an apparatus in which a conventional methodfor creating and recording the management information of a digital datastream can be employed;

FIG. 2 is a pictorial representation of the process of creating andrecording the management information of a digital data stream accordingto a conventional method;

FIG. 3 is a pictorial representation showing the hierarchical structureof a general recorded digital data stream;

FIG. 4 is a table showing the management information of a generalrecorded data stream;

FIG. 5 is a table showing a part of the management information of ageneral recorded data stream in detail;

FIGS. 6A and 6B are tables showing the time information of a generalrecorded data stream;

FIGS. 7A and 7B are tables showing the time information of a recordeddata stream according to an embodiment of the present invention;

FIG. 8 is a pictorial representation showing the relation between streamobject units (SOBUs) and time information according to an embodiment ofthe present invention;

FIG. 9 is the data format of the time information contained in a datastream header transmitted through the IEEE-1394 interface;

FIG. 10 is the data format of the packet arrival time of a digital datastream according to another embodiment of the present invention;

FIG. 11 is a block diagram of an apparatus for synchronizing twodifferent clock using the time information of a digital data streamaccording to another embodiment of the present invention; and

FIG. 12 is a timing diagram of certain nodes of the apparatus shown inFIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order that the invention may be fully understood, preferredembodiments thereof will now be described with reference to theaccompanying drawings.

FIGS. 7A and 7B depict the data formats of the stream start applicationpacket arrival time (S_S_APAT) and packet arrival time (PAT),respectively, in accordance with an embodiment of the invention. Thestream start application packet arrival time (S_S_APAT) is managementdata (navigation data) as shown in, e.g., FIG. 5. The packet arrivaltime (PAT) is time stamp information of data packets as shown in, e.g.,FIG. 3 and is the time information of user data as known.

Like a clock counting method and format thereof used when creating thedigital data stream, the 6-byte stream start application packet arrivaltime (S_S_APAT) contained in the stream object general information(SOB_GI) comprises a 9-bit packet arrival time extension (PAT_ext) and a39-bit packet arrival time base (PAT_base). The packet arrival timeextension (PAT_ext) is a modulo-300 counter that is incremented at arate of 27 MHz, whereas the packet arrival time base (PAT_base) isincremented at a rate of 90 kHz.

On the other hand, the packet arrival time (PAT) of a transport streampacket is 4-byte data comprising a 9-bit packet arrival time extension(PAT_ext) and 23-bit packet arrival time base (PAT_base). Like thestream start application packet arrival time (S_S_APAT), the packetarrival time extension (PAT_ext) is a modulo-300 counter that isincremented at a rate of 27 MHz and the packet arrival time base(PAT_base) is incremented at a rate of 90 kHz. The created packetarrival time (PAT) is included in each received transport stream packetto form stream object units to be recorded on a recording medium.

In consequence, the 4-byte packet arrival time (PAT) of a transportstream packet has the same format as the lower 4 bytes of the 6-bytestream start application packet arrival time (S_S_APAT) and so the lower4-byte data of the stream start application packet arrival time(S_S_APAT) always coincides with one of the recorded 4-byte packetarrival times (PATs). Also, there is certainly a packet arrival time(PAT) coinciding with the lower 4-byte data of the search time (ST)requested by a user, the 6-byte search time (ST) comprising a packetarrival time base (PAT_base) and a packet arrival time extension(PAT_ext) specified by the MPEG format.

It is also possible to record the packet arrival time (PAT) of eachtransport stream packet as 6-byte data like the stream start applicationpacket arrival time (S_S_APAT). When recording the packet arrival time(PAT), it is desirable to use a shorter data length, for example 4bytes, to improve the recording efficiency of the recording medium.However, a shorter data length of the packet arrival time (PAT)inevitably leads to a reduced range of the number that the packetarrival time (PAT) can represent. It will be shown below that thereduced range is no obstacle to searching for a requested packet.

The 4-byte packet arrival time (PAT) of a transport stream packet canrepresent up to 93.2 s (93.2=223/90 kHz) since its packet arrival timebase (PAT_base) is 23-bit data that is incremented at a rate of 90 kHz.The packet arrival time (PAT) is reset to zero when the value reachesthe limit, as shown in FIG. 9.

FIG. 8 shows the way the packet arrival time (PAT) of each transportstream packet created when a digital data stream received by a set topbox is recorded in the streamer 200. It is assumed that a stream objectunit (SOBU) is made up of 32 sectors with each sector being 2048 bytesand the transfer rate of the data stream is 10 kbps. Hence, the timethat elapses to record a stream object unit (SOBU) is 52.4 s (52.4=32sectors×2048 byte/10 Kbps) and the packet arrival time (PAT) is reset at93.2 s intervals. In other words, a stream object unit is created every52.4 s and the reset carry (PAT_carry) of the packet arrival time (PAT)is created every 93.2 s (93.2=223/90 kHz). As a result, the packetarrival times (PATs) of all transport stream packets belonging to astream object unit (SOBU) have mutually exclusive values as long as thetransfer rate of the digital data stream exceeds 10 Kbps.

The method for searching for the position(s) of a transport streampacket corresponding to a search time (ST) requested by a user from thedata stream recorded as shown in FIG. 8 will be explained with referenceto FIG. 2. First, the stream start application packet arrival time(S_S_APAT) contained in the stream object general information (SOB_GI)of each stream object (SOB) is compared with the requested search time(ST) and a stream start application packet arrival time (S_S_APAT) thatis closest to but does not exceed the request search time (ST) isdetected. Referring to the mapping list (MAPL) of the stream object SOB#1 corresponding to the detected stream start application packet arrivaltime (S_S_APAT), the incremental packet arrival times (IAPAT 1˜4)contained in the mapping list (MAPL) are summed up. The sum value ismultiplied by the unit time (x) and added to the stream startapplication packet arrival time (S_S_APAT). The procedure is repeateduntil the calculated value (S_S_APAT+x(Σ IAPAT) approaches the requestedsearch time (ST) without exceeding it. In FIG. 2, the summation andmultiplication is repeated to include IAPAT 4 because the calculatedvalue (S_S_APAT+x x(ΣIAPAT) exceeds the search time (ST) if thecalculation continues to IAPAT 5. The stream object corresponding to thecalculated value is SOBU 5, which corresponds to the upper 2-byte dataof the search time (ST) requested by a user.

From the start position A′ of the searched stream object SOBU 5, the4-byte packet arrival time (PAT) of each transport stream packet isdetected. The detected packet arrival times (PATs) are compared with thelower 4-byte data of the search time (ST) requested by a user to findthe transport stream packet (TS) the packet arrival time (PAT) of whichcoincides with the lower 4-byte data of the search time (ST).

Based upon the stream start application packet arrival time (S_S_APAT)and incremental application packet arrival time (IAPAT) in the mappinglist (MAPL), the stream object unit SOBU 5 corresponding to the upper2-byte data of the requested search time is detected first. Then, thepacket arrival time (PAT) of each transport stream packet constitutingthe stream object unit SOBU 5 is detected and compared with the lower4-byte data of the search time (ST) to find a desired transport streampacket. By the 2-step procedure, the transport stream packet located inthe recording position (S) corresponding exactly to the search time (ST)can be detected.

So far, the method for creating and recording the packet arrival time(PAT) of each transport stream packet on a recording medium has beenexplained with reference to an embodiment. In the embodiment, the formatof the created packet arrival time is compatible with that of the searchtime information recorded on the recording medium or requested by auser. In another embodiment of the invention to be explained from now,the packet arrival time (PAT) is created in such a way that the packetarrival time (PAT) is counted by count means comprising a bigger-unittime field and a smaller-unit time field so that the format of thepacket arrival time (PAT) is compatible with the clock format used indigital interfaces.

FIG. 9 is a pictorial representation of the syntax of a time stamp usedto transfer real-time data through the IEEE-1394 communicationinterface. The time stamp comprises a 12-bit cycle offset field, a13-bit cycle count field, and a 7-bit reserved field. The cycle offsetfield is incremented at a rate of 24.576 MHz and can represent up to 125μs by using 0˜BFF(h), whereas the cycle count field is incremented onceevery 125 μs and can represent up to 1 s by using 0˜1F3F(h). When thecycle offset field is reset to zero after counting up to BFF(h), a carryis generated and the cycle count is incremented by 1.

FIG. 10 shows the data format of the packet arrival time (PAT) inaccordance with the present invention. The format is intended forsynchronizing the packet arrival time (PAT) with the system clock of theIEEE-1394 communication interface whose counting format is shown in FIG.9 and comprises a 12-bit time offset field, a 19-bit time counter field,and 1-bit flag.

The time offset is incremented at a rate of 27 MHz, which is thestreamer clock. Like the cycle offset in the IEEE-1394 interface, it canrepresent up to 125 μs by using 0˜D2E(h). The time counter field isincremented at 125 μs intervals and can represent up to 65 s. Each timethe time offset field is reset after counting up to D2E(h), a carry isgenerated and the time counter field is incremented by 1.

The 1-bit flag indicates whether or not a program clock reference (PCR)is contained in the corresponding transport stream packet. In thisexample, the value “1” indicates that the transport stream packetcontains a program clock reference. On the contrary, the value “0”indicates that the corresponding transport stream packet only containsthe time counter and time offset of the packet arrival time createdbased upon the streamer clock.

Referring to FIG. 11, a counter 83 cyclically counts the output pulse ofvoltage-controlled oscillator (VCO) 81 from 0 to 3374 using lower 12bits (b11˜b0).

When digital data is outputted from a digital receiving processing unit210 in the streamer 200 (FIG. 1), a time stamp detector 71 detects thetime stamp of the IEEE-1394 interface contained in each transport streampacket and transfers the detected time stamp to a time counter triggerunit 73. Time counter trigger unit 73 generates a pulse such as {circlearound (0)} shown in FIG. 12 each time the state of the leastsignificant bit (b12) of the time counter field of FIG. 10 changes from“1” to “0” or from “0” to “1”.

The output pulse of time counter trigger unit 73 is connected to theclock of a T flip-flop 75. T flip-flop 75 toggles the output Q on thepositive edge of the clock pulse. The output Q of T flip-flop 75, whichis a 4 kHz pulse figured as {circle around (2)} in FIG. 12, is connectedto an input of a phase difference detector 77. The 13th bit (b12) ofcounter 83 is also a 4 kHz pulse and is connected to another input ofphase difference detector 77. Phase difference detector 77 compares thephases of the two input pulses and outputs an error signal correspondingto the phase difference. The high-frequency components of the errorsignal is filtered by a low-pass filter 79 and the low-pass filterederror signal is applied to the voltage-controlled oscillator 81. Inresponse to the filtered error signal, the voltage-controlled oscillator81 adjusts its 27 MHz oscillation frequency.

In consequence, the packet arrival time of each transport packettransmitted based upon the time stamps of the IEEE-1394 interface addedto the header of the transport stream packet is created and recordedbased upon a clock of 27 MHz synchronized with the time stamp clock of24.576 MHz, thereby preventing the time intervals between twoconsecutive transport packets from being distorted by transmission.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

1. An apparatus for recording time information associated with digitaldata, comprising: a time information creating unit creating a first timefield and a second time field, wherein the first time field includes a90 KHz unit value and the second time field includes a 27 MHz unitvalue; and a data formatter creating a data object unit beingpresentation data by adding a corresponding unit of the digital data tomanagement data including the time information.
 2. The apparatus ofclaim 1, wherein the first time field comprises a base part of the timeinformation and is created by a 90 KHz unit, while the second time fieldcomprises an extension part of the time information and is created by a27 MHz unit.
 3. The apparatus of claim 1, wherein the data object unitincludes video data, and the time information is set to a presentationstart time of the video data in the data object unit.
 4. The apparatusof claim 1, wherein the first time field comprises a plurality of bytes,wherein at least one byte includes a portion of a bigger-unit time fieldand a portion of a smaller-unit time field.
 5. The apparatus of claim 1,wherein the corresponding unit comprises one or more packets.
 6. Theapparatus of claim 1, further comprising: a recording unit recording thedata object unit to a recording medium, wherein the management data isfollowed by the corresponding unit.
 7. The apparatus of claim 1, whereinthe data formatter further creates data object including one or moredata object units.
 8. The apparatus of claim 7, further comprising: arecording unit recording the data object to a recording medium, whereinthe management data is followed by the corresponding unit.
 9. A methodof recording time information associated with digital data, comprising:creating a time information including a first time field and a secondtime field, wherein the first time field includes a 90 KHz unit valueand the second time field includes a 27 MHz unit value; and creating adata object unit being presentation data by adding a corresponding unitof the digital data to management data including the time information.10. The method of claim 9, wherein the first time field comprises a basepart of the time information and is created by 90 KHz unit, while thesecond time field comprises an extension part of the time informationand is created by a 27 MHz unit.
 11. The method of claim 9, wherein thedata object unit includes video data, and the time information is set toa presentation start time of the video data in the data object unit. 12.The method of claim 9, wherein the first time field comprises aplurality of bytes, wherein at least one byte includes a portion of abigger-unit time field and a portion of a smaller-unit time field. 13.The method of claim 9, wherein the corresponding unit comprises one ormore packets.
 14. The method of claim 9, further comprising: recordingthe data object unit to a recording medium, wherein the management datais followed by the corresponding unit.
 15. The method of claim 9,wherein the data formatter further creates data object including one ormore data object units.
 16. The apparatus of claim 15, furthercomprising: recording the data object to a recording medium, wherein themanagement data is followed by the corresponding unit.
 17. A recordingmedium including time information associated with digital data,comprising: a recording layer; and data object units recorded on therecording layer, wherein the data object units being presentation dataare created by adding a corresponding unit of the digital data tomanagement data including a time information, wherein the timeinformation includes a first time field and a second time field, whereinthe first time field includes a 90 KHz unit value and the second timefield includes a 27 MHz unit value.
 18. The recording medium of claim17, wherein the first time field comprises a base part of the timeinformation and is created by a 90 KHz unit, while the second time fieldcomprises an extension part of the time information and is created by a27 MHz unit.
 19. The recording medium of claim 17, wherein the dataobject unit includes video data, and the time information is set to apresentation start time of the video data in the data object unit. 20.The recording medium of claim 17, wherein the first time field comprisesa plurality of bytes, wherein at least one byte includes a portion of abigger-unit time field and a portion of a smaller-unit time field. 21.The recording medium of claim 17, wherein the corresponding unitcomprises one or more packets.
 22. The recording medium of claim 17,wherein the management data is followed by the corresponding unit. 23.The recording medium of claim 17, further comprising: a data objectincluding one or more data object units, wherein the management data isfollowed by the corresponding unit.
 24. A method of reproducing digitaldata, comprising: (a) reading management data associated with a dataobject unit including video presentation data, wherein the managementinformation includes a time information comprising a first time fieldand a second time field, and the first time field includes a 90 KHz unitvalue and the second time field includes a 27 MHz unit value; and (b)reproducing the data object unit based on the time information.
 25. Themethod of claim 24, wherein the first time field comprises a base partof the time information and is created by a 90 KHz unit, while thesecond time field comprises an extension part of the time informationand is created by a 27 MHz unit.
 26. The method of claim 24, wherein thetime information is set to a presentation start time of the videopresentation data in the data object unit.
 27. The method of claim 24,wherein the first time field comprises a plurality of bytes, wherein atleast one byte includes a portion of a bigger-unit time field and aportion of a smaller-unit time field.
 28. The method of claim 24,wherein the data object unit comprises one or more packets.